Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
FIG. 5 is a diagram showing part of circuitry of a typical LCD. The LCD 10 includes a first substrate (not shown), a second substrate (not shown) facing the first substrate, a liquid crystal layer (not shown) sandwiched between the first substrate and the second substrate, a gate driver (not shown), and a source driver (not shown).
The first substrate includes a number n (where n is a natural number) of scanning lines 11 that are parallel to each other and that each extend along a first direction, and a number k (where k is also a natural number) of data lines 12 that are parallel to each other and that each extend along a second direction orthogonal to the first direction. The first substrate also includes a plurality of thin film transistors (TFTs) 13 that function as switching elements. The first substrate further includes a plurality of pixel electrodes 15 formed on a surface thereof facing the second substrate. Each TFT 13 is provided in the vicinity of a respective point of intersection of the scanning lines 11 and the data lines 12.
Each TFT 13 includes a gate electrode 131, a source electrode 132, and a drain electrode 133. The gate electrode 131 is connected to the corresponding scanning line 11. The source electrode 132 is connected to the corresponding data line 12. The drain electrode 133 is connected to a corresponding one of the pixel electrodes 15.
The second substrate includes a plurality of common electrodes 16 opposite to the pixel electrodes 15. In particular, the common electrodes 16 are formed on a surface of the second substrate facing the first substrate, and are made from a transparent material such as ITO (indium-tin oxide) or the like. A pixel electrode 15 and a common electrode 16 facing the pixel electrode 15 form a capacitor 17. A pixel electrode 15, a common electrode 16 facing the pixel electrode 15, and liquid crystal molecules of the liquid crystal layer sandwiched between the two electrodes 15, 16 cooperatively define a single pixel unit (not labeled). Each TFT 13 drives a corresponding pixel unit.
When the LCD 10 works, the gate driver provides a scanning voltage to the gate electrode 131 of the TFT 13 via the corresponding scanning line 11, and activates the TFT 13. The source driver provides a gradation voltage to the pixel electrode 15 via the source electrode 132 and the drain electrode 133 of the activated TFT 13 when the scanning line 11 is scanned, thus producing a potential difference between the pixel electrode 15 and the corresponding common electrode 16. The liquid crystal molecules between the pixel and common electrodes 15, 16 are twisted to let light penetrate therethrough. The degree of twisting is proportional to the gradation voltage. In this way, all the pixel units produce various degrees of light penetration, which together make up an image that is displayed on a screen of the LCD 10.
The scanning lines 11 are generally very thin, and therefore have relatively high essential resistances. When the scanning voltages flow through the scanning lines 11, voltage drops tend to occur. In particular, the voltage drop increases with increasing distance away from the gate driver. That is, a voltage driving a TFT 13 distal from the gate driver is frequently less than a voltage driving a TFT 13 close to the gate driver. Thus, the LCD 10 may have a degraded display performance.
Therefore, a new LCD that can overcome the above-described deficiencies is desired.